Log Schema Audit

Audit newline-delimited JSON logs against a contract, and across the whole set. The two findings that need every line at once: a field whose type varies between lines, so an index either rejects the minority or coerces them silently; and a message field with nearly as many distinct values as lines, which is interpolated rather than templated so nothing groups and cost scales with volume. Also reports absent required fields, a level differing only in case, and a timestamp with no offset.